Control apparatus for resonant type jet engines



Allg. 24, 1954 LEEYIL 2,687,009

CONTROL APPARATUS lFOR RESONNT TYPE JEU` ENGINES Filed sept. 2U, 1947' Y INVENTOR Faa /fv [ey/Walz Leal?.

ATTORNEY Patented Aug. 24, 1954 CONTROL APPARATUS FOR RESONANT TYPE JET ENGINES Leighton Lee II, Rocky Hill, Conn., assignor to Niles-Bement-Pond Company, West Hartford, Conn., a corporation of New Jersey Application September 20, 1947, Serial No. '775,322

9 Claims. l The present invention relates to control apparatus for internal combustion engines, and

especially to engines of the type in which the combustion chamber `pressure varies cyclically. It is of especial utility in connection with engines of the resonant jet type, and is shown in connection with such `an engine, although it may be used with other types of combustion engines.

In the resonant jet type of engine, fuel and air are supplied to the combustion chamber at predetermined rates. Combustion is initiated either by a continuously supplied spark or upon contact of a combustible mixture with the hot Walls of the combustion chamber. When combustion occurs, the resulting high pressure in the combustion chamber operates suitable valve mechanism provided for the purpose of cutting 01T the air supply. The combustion chamber pressure is then momentarily greater than the fuel supply pressure, so that the fuel supply is effectively cut on', also. The products of combustion expand out through the exhaust passage, producing the jet which propels the engine. As soon as the combustion chamber pressure falls off suiiciently, the air valves open, the fuel supply resumes, and the cycle is repeated.

In such engines, the greatest thrust is obtained when the highest pressure is produced in the combustion chamber. For maximum thrust, it is therefore desirable to control the fuel supply so as to maintain the peak combustion chamber pressure at a maximum value.

This maximum peak combustion chamber pressure does not, however, represent the most eicient engine operating condition. The maximum eciency occurs when the peak combustion chamber pressure is at some lower value which depends upona number of other factors, such as engine design, atmospheric pressure, etc.

It is desirable to operate an engine of this type either at its maximum thrust or at its maximum emciency. For example, if used in a flying bomb, it is desirable to use maximum thrust at take-off and when nearing the destination. At other times, it is desirable to use the most eii'icient power in order to obtain the maximum range with a given fuel supply.

It is therefore an object of the present invention to provide an improved fuel supply system for a resonant jet type internal combustion engme.

, A further object is to provide a fuel supply system which may be operated to maintain a selected combustion chamber pressure.

A further object is to provide a system which will maintain the maximum combustion chamber pressure.

A further object is to provide a system which will selectively maintain either a predetermined combustion chamber pressure or maximum combustion chamber pressure.

Other objects and advantages of my invention will become apparent from a consideration of the appended specification, claims and drawing, in which Figure 1 illustrates, somewhat diagrammatically, a fuel supply control system for a resonant jet engine, embodying some of the principles of my invention, and adapted to maintain a selected peak pressure in the combustion chamber, and

Fig. 2 illustrates, somewhat diagrammatically, a more elaborate fuel supply control system which selectively maintains either a predetermined peak combustion chamber pressure or maximum peak combustion chamber pressure.

Figure 1 There is shown in Fig. 1 a portion of a combustion chamber I 0 of a resonant or intermittent type jet engine. Extending across the inlet side of the chamber IIJ is a grille l2 through which projects a series of nozzles I4. Between the nozzles are located horizontal louvers I6. Attached to each of the louvers I6, and to each of the nozzles I4, are a series of exible vanes I8. These vanes are designed to open when the air pressure on the entrance side of the grille I2 is greater than the pressure in the combustion chamber, and to close when the combustion chamber pres- Sure is greater. They are shown in their closed position.

Fuel is supplied to the nozzles I4 through a manifold 20, which receives fuel from a regulating valve unit generally indicated at 22.

Fuel for the engine comes from a tank (not shown) and ows through a conduit 24, past a valve 26, a chamber 28 in the valve unit 22 and thence through a conduit 30 to manifold 20 and nozzles I4. The valve 26 is attached by a stem 32 to a exible diaphragm 34 which separates chamber 28 from a chamber 36. A spring 3B within the chamber 36 biases the valve 26 toward closed position.

The position of the regulating valve 26 is determined by a control or pilot valve unit generally indicated at 40. The control valve unit 40 includes a piston valve 42 positioned by a diaphragm 44 which separates a pair of expansible chambers 46 and 48. The diaphragm 44 and Valve 42 are biased to the right by means of a of a screw 52.

The chamber 46 is vented to atmosphere as indicated at 54. The chamber 48 is connected through a check valve 56 and a conduit '56 to the combustion chamber I0. A Xed restriction 60 is connected in parallel with the check valve 66. Although the restriction 60 and valve 56 are shown as separate structures for the purpose of this diagrammatic drawing, it may be preferable to use a simple check valve with a notch in its seat to provide a slight leak through it at all times.

Operation of Figure 1 The particular peak combustion chamber pressure which the system is to maintain may be selected by manipulation of the adjusting screw 62. The check valve 56 is designed as to size and spring loading so that it opens only when the combustion chamber pressure approaches its peak value. The restriction 60 is much smaller than the opening in the check valve 66, so that each explosion in the combustion chamber causes valve 56 to open momentarily, thereby discharging fluid at the combustion chamber pressure into chamber 48. As the pressure in the combustion chamber drops off, the fluid in chamber 40 leaks out through restriction 60. The rate of leakage is so designed with respect to the frequency of explosions in the engine that the next explosion builds up the pressure in chamber 48 again before it has decreased materially from the pressure existing during the explosion.

The rate at which the explosions follow each other in the combustion chamber is relatively high compared to the mass of diaphragm 44 and valve 42, so that the cyclical variations in pressure in chamber 4S due to the explosions do not cause substantial variations in the position of valve 42. The pressure in chamber 46 is therefore a measure of the average peak combustion chamber pressure.

The effective area of diaphragm 34 is made substantially equal to that of valve 26. Hence the pressure in chamber 28 acts in opposite directions against equal areas so that valve 26 is balanced against the pressure in chamber 28. The inlet pressure above valeve 26 acts in an opening direction on it, and the pressure in chamber 36 acts on diaphragm 34 in a valve-closing direction. The latter pressure is supplemented by the force of spring 38.

When the average peak combustion chamber pressure falls below the value determined by i the setting of spring 50, that spring moves valve 42 to the right, thereby admitting fuel at the pressure in chamber 28 through conduit 66, past valve 42 and through conduit 64 to chamber 36. The pressure in chamber 36 is thereby made substantially lower than the inlet pressure acting downward on valve 26, so that the valve is moved in an opening direction. This movement continues until the increased fuel supply is suiiicient to restore the combustion chamber pressure to its previously selected value.

If the average peak combustion chamber pressure increases above the desired value, the diaphragm 44 and valve 42 are moved to the left, thereby admitting fuel at inlet pressure through conduit 62 past valve 42 into conduit 64 and chamber 36. 'Ihe pressure in chamber 36 is thereby made equal to the inlet pressure acting downwardly on valve 26, and the spring 38 moves valve 26 toward closed position to decrease the |20 connected to Valve ||0 by a stem |22.

fuel flow to the engine and restore the combustion chamber pressure to its selected value.

Figure 2 There is shown in Fig. 2 a system which may operate either to maintain maximum combustion chamber pressure or to maintain a selected value of combustion chamber pressure.

A fuel regulator generally indicated at |06 is controlled by selector valve units |02 and |04. The selector valve |02 operates in response to the combustion chamber pressure, while selector valve |04 operates in response to the rate of flow of fuel to the engine.

Fuel comes from a tank (not shown) and flows through a conduit |06, a chamber |08 in the fuel regulator |00, past a valve ||0, through a conduit ||2 and through a spring loaded .discharge valve I4 into the combustion chamber H6. The valve H4 is biased closed by means of a spring H6, and opens increasingly as the fuel pressure on its upstream side increases.

The fuel regulator includes a diaphragm A tension spring |24 biases the valve H0 toward open position. The diaphragm separates chamber |00 from a chamber |26.

The fuel regulator |06 includes a diaphragm |20 connected to valve ||6 by a stem |22. A tension spring |64 biases t1 e valve H6 toward open position. The diaphragm |20 separates chamber |06 from a chamber |26.

The selector Valve unit |62 includes a diaphragm |23 separating a pair of expansible chambers and |32. Attached to the center of diaphragm |26 is a piston valve |34. Chamber is connected through a conduit |36, and a check valve |38 with a parallel restriction |40, and a conduit |42 to the combustion chamber H6. The check valve |63 and restriction |40 correspond'to the check valve 56 and restriction 60 of Fig. 1. Chamber |32 is connected through a Fixed restriction |44 to the conduit |36. Chamber |32 is also connected through a conduit |66 to a vent valve |46 which is biased to open posi*- tion by a spring |50, and which may be operated to closed position by a cam |52. A spring |54 is retained between the right end of valve |34 and a retainer |56 which engages cam |52.

The selector valve |04 includes a diaphragm |66 separating a pair of expansible chambers |60 and |62. The diaphragm |60 is attached at its center to a piston valve |64. A spacer block |66 lies `between the valve |64 and the cam |52. A series of stops |66 limit the leftward movement of diaphragm |58.

Chamber |66 is connected through a conduit |10, a check valve |12 in parallel with a fixed restriction |14, and a conduit |16 to the fuel com duit l2. Check valve |12 and restriction |14 are similar in structure and function to check valve 60 and restriction 56 of Fig. l. They are required in this case because of the cyclical vari ation of fuel pressure due to opening and clos ing of valve H4. The chamber |62 is connected through a restriction |16 to the conduit |10.

When the cam |52 is in the position shown in the drawing, spacer |66 holds the valve |64 near the right-hand end of its range of movement. The chamber |26 in the fuel regulator |00 is then connected through conduit |80, restriction |02, past valve |64, and through conduit |84 to a port adjacent the valve |34 and thence past valve |34 and through conduits and |16 to the conduit ||2.

The effective area of diaphragm |20 isysubstantially the same as that of valve so that the valve is balanced against the pressure in chamber |08. Since, as `above described, chamber |26 is connected through selector valves |04 and |02 to conduit |I2, the pressure in that conduit acts on diaphragm |20 in a valve closing direction. It is opposed by the same pressure in conduit ||2 acting in an opening direction di` Vrectly on valve ||0 and by the force of tension spring |24. Spring |24therefore moves the valve inan opening direction, since `the pressures acting on the valve are all balanced.

. When cam |52 is in the position shown, vent valve |48 is open, so that `the pressure in chamber |32 is atmospheric. The pressure in chamber I 30 is the combustion chamber pressure, as modified by check valve |38 and restriction |40. Cam |52 has moved retainer` |56 to a position where spring |54 actively biases valve |34 toward the left.

When the combustion chamber pressure has a certain value, determined by the strength of spring |54, the valve |34 is positioned so that it blocks the port leading to conduit |84. The fluid within chamber |26 is then trapped there and the pressure therein remains constant. When the combustion chamber pressure exceeds that predetermined value, valve 34 moves to the right,`

connecting conduit |84 through conduit |86 with chamber |08. This increases the pressure in chamber |26 to equal that in chamber |08. Valve ||0 is then moved toward closed position by the pressure differential acting in opposition to spring |24. This decreases the fuel flow, thereby decreasing the combustion chamber pressure again to its selected value. When the `combustion chamber pressure falls below the desired value, valve |34 moves toward the position-shown in the drawing, thereby `connecting chamber |26 with conduit ||2, so that spring |24 moves valve I Il toward open position, thereby increasing the fuel fiow so as torestore the combustion chamber pressure to the desired value.

When it is desired to operate the engine at maximum power rather than maximum efficiency, the cam |52 is rotated through 90. This closes the vent valve |48, and relieves the `force of spring |54 previously acting on valve |34. At the same time, the spacer |66, which limited the leftward movement of valve I 64 is removed as an effective stop.

"Selector valve unit |04 now is operated in accordance with the rate of change of fuel pressure in conduit ||2. In other Words, if the pressure in conduit I I2 is increasing, then the pressure in chamber |60 exceeds that in chamber |62, because of the effect of restriction |'|8` in delaying the increase of pressure in chamber |62, so that valve |64 is moved to the dotted line position shown in the drawing. However, if the pressure in conduit I|2 is decreasing, then the pressure in chamber |62 exceeds that in chamber |60, so that valve |64 is moved to the full line position shown in the drawing wherein conduit |80 is connected to conduit |84.

Because of the closing of vent valve |48, the restriction |44 is now effective to modify the pressure in chamber |32, so that selector valve unit |02 now responds to the rate of change of combustion chamber pressure rather than to the difference between that pressure and atmospheric pressure.

The dimensions and characteristics of spring |54 are such that it is removed completely as an influence` on the position of valve |34 when the cam |52 is rotated through 90.

Under these conditions, the system operates to alternately increase or decrease the fuel flow so as torcause the combustion chamber pressure to hunt about its maximum pressure. There is a certain value of fuel ow which Will produce the maximum combustion chamber pressure. Increase of the `fuel ow above this value will decrease the combustion chamber pressure because of the enriching of the combustible mixture will produce less complete combustion. Likewise, a decrease in theamount of fuel ow will decrease the combustion chamber pressure.

Consider the cycle of operations which ensues when the cam |52 is rotated for maximum thrust, if the fuel ow and combustion chamber pressure are both increasing at that time. The increase in fuel ow causes the valve |64 to move to the left to the position shown in dotted lines in the drawing, so that conduit is connected to conduit |90. The increase in combustion chamber pressure moves the valve |34 to the right so that conduit is connected to conduit |16 and thence to conduit ||2. The pressure in chamber |26 is then the same as in conduit |I'2 and valve I|0 therefore continues to move in a fuel flow increasing direction under the influence of spring |24. i

The fuel iiow continues to increase until the average peak combustion chamber pressure reaches its maximum and starts to decrease again. When that happens, valve |34 is moved to the left, thereby connecting conduit |90 with conduit |86. This connects chamber |26 to chamber |08, thereby reversing valve II 0 and starts the fuel flow decreasing with the result that the combustion chamber pressure again starts to increase. As soon as the fuel flow starts to decrease, valve |64 moves to the right, thereby connecting conduit |80 with conduit |84, and the increasing combustion chamber pressure substantially simultaneously moves valve |34 to the right, connecting conduit |84 with conduit |86, and hence with chamber |08. This connection keeps the fuel flow decreasing until the maximum combustion chamber pressure is again reached. When the combustion chamber pressure starts to decrease from the maximum, valve |34 again reverses itself and moves to the left, thereby connecting conduit |84 with conduit |88 and starting the fuel flow increasing again. When this happens, the valve |64 is again moved to the right,.connecting conduits |80 and |84. Substantially simultaneously, the combustion chamber pressure begins to increase because of the increased fuel flow, and valve |34 moves again to the right, connecting conduits I8'4 and |86, so that the fuel iiow continues to increase. andmay start over again.

Th-e restriction |82 is provided to slow the motion of the main fuel valve ||0 so as to prevent it from responding too quickly at a time when the valves |34 and |64are moving simultaneously.

The terms and expressions which I have employed are used as terms of description and not of limitation, and I have nointention, in the use of such terms and expressions, of excluding any equivalents of the features shown andv described or portions thereof, but recognize that various` modifications are possible within the scope of the invention claimed.

. I claim as my invention:

1. Fuel supply control apparatus for an inter- The cycle is now complete,

nal combustion engine having incorporated therein a combustion chamber in which the pressure varies cyclically with the operating cycle of said engine, comprising fuel flow controlling valve means, an operator for said valve means, means for generating a fluid pressure indicative of the average maximum pressure in said combustion chamber, pressure sensitive means, responsive only to said fluid pressure, for controlling said operator in accordance With said pressure; said pressure generating means including an expansible chamber adjacent said pressure sensitive means, a conduit connecting said expansible chamber and said combustion chamber, a checl; valve in said conduit for permitting flow therethrough whenever the pressure in the combustion chamber exceeds the pressure in the expansible chamber by a predetermined amount, and a fixed restriction connected in parallel with said check valve for permitting a retarded flow from the expansible chamber to the combustion chamber Whenever the combustion chamber pressure is lower than the expansible chamber pressure, said check valve and restriction cooperating to vary the pressure in said expansible chamber as a function of the maximum value of the cyclically varying pressure in said combustion chamloer.

2. Fuel supply control apparatus for an internal combustion engine having incorporated therein a combustion chamber in which the pressure varies cyclically with the operating cycle of said engine, comprising fuel flow controlling valve means, an operator for said. Valve means, means for generating a fiuid pressure indicative of the average maximum pressure in said combustion chamber, pressure sensitive means, responsive only to said fluid pressure, for controlling said operator in accordance with said pressure; said pressure generating means including an expansible chamber adjacent said pressure sensitive means, conduit means connecting said combustion chamber and said expansible charnber, a check valve in said conduit means opening in the direction of flow toward said expansible chamber, and a fixed restriction connected in parallel with said check valve.

3. Fuel supply control apparatus for an internal combustion engine, comprising a fuel flow controlling valve, means biasing said valve in one direction, a fluid motor for operating said valve against said biasing means, a first source of fluid at a pressure high enough to overcome said biasing means when supplied to said fluid motor,

a second source of fluid at a substantially lower pressure, a first selector valve, means responsive to the direction of change of the pressure in the combustion chamber of said engine for operating said selector valve to a first position when said pressure is increasing and to a second position when said pressure is decreasing, a second selector valve, means responsive to the direction of change of the rate of fuel now to said engine for operating said second selector valve to a. first position when said fuel flow is increasing and to a second position When said fuel flow is decreasing, and means including both said selector valves for connecting said motor selectively to said sources, said connecting means being effective when both selector valves are in corresponding -positions to cause operation of said fuel ow controlling valve in a fuel now increasing direction and when said selector valves are in opposite positions to cause operation of said fuel iiow controlling valve in a fiuel flow decreasing direction.

4. Fuel supply control apparatus for an internal combustion engine, comprising fuel iiow controlling means, means for operating said fuel flow controlling means, means for controlling said operating means, and means for rendering said last controlling means selectively responsive only to either the pressure in a combustion chamber in said engine or to the direction of change of said pressure, whereby said fuel flow is controlled in accordance with either said pressure, or its. direction of change.

5. Fuel supply control apparatus for an internal combustion engine, comprising fuel flow controlling valve means, means for operating said valve means including a pair of expansible chambers separated by a movable Wall, means operatively connecting said Wall and said valve means, means for supplying to one of said chambers a iuid at a pressure indicative of the pressure in a combustion chamber of said engine,

means forming a vent for maintaining the otherV chamber substantially at atmospheric pressure, a spring acting on said Wall in opposition to the pressure in said one chamber, and a restricted passage connecting said chambers.

6. Fuel supply control apparatus as in claim 5, comprising means for closing said vent to make said operating means responsive to the rate of change of pressure in said combustion chamber.

7. Fuel supply control apparatus as in claim 6,'

comprising means for relieving the force of said spring simultaneously with th eclosure of said vent so that said Wall moves to one end or the other of its range of travel, depending upon the direction of change of said combustion chamber pressure.

8. Fuel supply Control apparatus as in claim 7, in which said fuel now controlling valve means includes a fuel conduit, a valve in said fuel conduit, and hydraulic motor means for positioning said valve, said operating means includes a pilot valve for controlling said motor means, and said connecting means connects said Wall and vsaid pilot valve. f

9. Fuel supply control apparatus as in claim 8, comprisinga` second pilot valve cooperating with said first-mentioned pilot valve to control said hydraulic motor means, means responsive to the rate of now of fuel to said engine for operating said second pilot valve to one end or the other of its range of travel depending upon the direction of change of said rate of fuel flow, and means movable concurrently with said vent closing means and effective when said vent is open to move said second pilot valve to one end of its range of travel and hold it there, so thatl said hydraulic motor means is then controlled by said first-mentioned pilot valve acting alone.

References Cited in the le of this patent UNTIED STATES PATENTS Klinge Mar. 20, 1951 

